I have a page that uses Ajax Page Methods. When the page first loads, the user is prompted to select a year. This is the only time that a PostBack occurs. The year is stored in a private static page-level integer property named SelectedYear. There are several page methods that pass data from the client to the server, but the year is always stored on the server, so that it won't have to be to be passed in again. The problem is, in a few cases, within the server WebMethod, the SelectedYear property seems to be reverting to 0. I can test for 0 and throw the error back to the client, but it would help if I could explain why it happened. At this point, I don't know. Any ideas? I'm a bit new to this style of programming. Here's a (very simplified) example of the code. The user MUST have selected a year in order to ever have reached the save function.
Here is my C# server code:
public partial class Default : System.Web.UI.Page
{
private static int SelectedYear;
protected void YearSelected(object sender, EventArgs e)
{
if (sender.Equals(btnCurrentYear))
SelectedYear = 2013;
else
SelectedYear = 2014;
}
[WebMethod]
public static bool Save(string FirstName, string LastName)
{
try
{
if (HttpContext.Current.User.Identity.IsAuthenticated)
//Right here, SelectedYear is sometimes 0.
SaveApplication(FirstName, LastName, SelectedYear);
else
throw new Exception("User is not logged in.");
}
catch (Exception ex)
{
throw;
}
}
}
Here is my JavaScript client code:
function Save(FirstName, LastName) {
PageMethods.Save(firstName, LastName, SaveSucceeded, SaveFailed);
}
function SaveSucceeded(result) {
//Notify user that save succeeded.
}
function SaveFailed(error) {
//Notify user that save failed.
}
Your problem is this:
private static int SelectedYear;
You'll want to remove the static. Static means it's global and will be shared for all users/requests... so when you set it to 2013 for one user, and another user hits that page who hasn't yet selected a year, it will be set to 0... for both of them. Yikes!
Trace through your postbacks to see what is happening to that variable during your AJAX methods.
You should consider storing the value in a session variable or maybe in a hidden field on the page.
More reading on a similar post: ASP.NET C# Static Variables are global?
Related
This is my controller code:
private string testVal;
public ActionResult Index()
{
testVal = "test";
return View();
}
public ActionResult NextView()
{
if (testVal == null)
Debug.WriteLine("testVal is null");
return View();
}
Is it possible to remeber values like testVal after changing page? It seems that when redirecting it resets values (testVal in NextVal is null).
Edit:
I try to save values to session but Session is null. I am using SignalR and when user is connected to page i use static event from hub to inform controller that user has connected - but inside method that runs on that event Session is unfortunetly null.
My controller code:
public ActionResult Index()
{
LoadingHub.userConnected += new EventHandler<IdEventArgs>(UserConnected);
return View();
}
private void UserConnected(object sender, IdEventArgs e)
{
Debug.WriteLine("User Connected with Id: " + e.Id);
if (Session == null)
Debug.WriteLine("Session is null");
}
My signalr hub:
public class LoadingHub : Hub
{
public static event EventHandler<IdEventArgs> userConnected;
//Function informs server that user has connected
public void Connected()
{
Debug.WriteLine("Hub Connected Method");
var id = Context.ConnectionId;
userConnected(this, new IdEventArgs(id));
}
}
Every time that you make a request a new instance of the controller is created so using a private field you will not be able to retain the value of this variable.
The easiest way for you to retain it it is to use a session. (if you want to retain this value per user base)
for example in your code
public ActionResult Index()
{
System.Web.HttpContext.Current.Session["testVal"] = "test";
return View();
}
public ActionResult NextView()
{
if (System.Web.HttpContext.Current.Session["testVal"] == null)
Debug.WriteLine("testVal is null");
return View();
}
you can use cookie or cache to replace the variable.
when you redirect to a webpage ，the controller will be newed ,so you cannot get the right testVal .but the cookie is stored in broswer .so you can set it and get .
You may use session or Pass the data to the controller
Have you looked into ASP.NET server side state management click here.
These are basically different ways to remember a value on the server once a new page has been loaded.
So a few server side techniques you could use to remember testVal are Session State or Application State. However Session State is more suitable for your scenario as it is only specific to the user's current session whereas Application State stores data that can be shared between sessions and would therefore be more ideal for global variables.
You can read the link I provided to read more on the differences though.
I would also like to warn you (as some say to use cookies), the user can delete or disable or manipulate them on the browser so this isn't an ideal solution.
Since I'm a newbie for asp, I'm trying to take a name as input,trying to put that name in list, then check the list to find a match. I'm doing this as basics keeping the log in procedure in mind, which I will try to implement later. I have the following code:
I have made a class like this:
public class Login
{
public string name { get; set; }
}
The two button events are as follows:
List<Login> list;
protected void Button1_Click(object sender, EventArgs e)
{
list = new List<Login>(){
new Login { name = TextBox1.Text },
new Login { name = "Badhon"}
};
Label1.Text = "Inserted";
}
protected void btnLogIn_Click(object sender, EventArgs e)
{
foreach (var s in list)
{
if (s.name == TextBox1.Text)
{
Label1.Text = "Found";
break;
}
else
Label1.Text = "Not Found";
}
}
when I'm trying to insert,its working fine, but when clicking on the login button showing any error message like "Object reference not set to an instance of an object."
When you press the login button you're in a different scope to when you pressed the first button, so the list is not initialised (Each time you press an ASP button you get a new state: The web is designed to be stateless).
Why not use the asp:login control?
You code is not exactly what it is supposed to be. You'd better go searching for some (of the various) examples on how to hanle logins in ASP.NET.
Each click is a new HTTP request. The list initialized in the first request is not the same with the list in the other request because each request will use its own instance of the Page object.
You need to read & understand the life cycle of a ASP.net page: http://msdn.microsoft.com/en-us/library/ms178472.aspx
make protected properties to store list of logins
It should looks like this:
protected List<Login> LoginStore
{
get{ return ViewState["store"] =! null ? (List<Login>)ViewState["store"] : new List<Login>; }
set{ ViewState["store"]=value; }
}
You can use Session as well as ViewState. It will make your list doesn't disapear every time you make PostBack.
then in event btnLogIn
create List<Login> list = LoginStore;
then make the rest of your code.
click on here
why do go forloop, use session variables in Global.asax, try googlin you can find many example..
I have an mvc 3 app for which I'm implementing authorization using my own login view which checks if the users name and password are allowed and then sets a variable in the session to say that the user is loggged in. This kind of works but for one particular view it is behaving in a strange undesirable way. The said view contains a form which I use to input some data and upload a file. For some reason which I can't figure out, after this form is posted a new session is started and therefore the variable which remembered that the user was logged in is reset to false and subsequently the login page is displayed again.
I'm lost as to why the application is starting a new session at this point? I have not instructed it to do this. Can anyone recommend solutions to stop this behaviour and get it to keep the old session?
Thanks.
UPDATE - Some Code:
Note the session seems to be terminated immediately after the response to the posted Create form
CMS controller which uses a custom Autorize attribute called "RDAutorize" on all actions:
[RDAuthorize]
public class PhotoCMSController : Controller
{
public ActionResult Create()
{
/* Code omitted: set up a newPhoto object with default state */
/* Display view containing form to upload photo and set title etc. */
return View("../Views/PhotoCMS/Create", newPhoto);
}
[HttpPost]
public ContentResult Upload(int pPhotoId)
{
/* Code ommited: receive and store image file which was posted
via an iframe on the Create view */
string thumbnail = "<img src='/path/to/thumb.jpg' />";
return Content(thumbnail);
}
[HttpPost]
public ActionResult Create(string pPhotoTitle, string pCaption etc...)
{
/*Code omitted: receive the rest of the photo data and save
it along with a reference to the image file which was uploaded
previously via the Upload action above.*/
/* Display view showing list of all photo records created */
return View("../Views/PhotoCMS/Index", qAllPhotos.ToList<Photo>());
/* **Note: after this view is returned the Session_End() method fires in
the Global.asax.cs file i.e. this seems to be where the session is
being lost** */
}
}/*End of CMS Controller*/
Custom Authorize action filter:
public class RDAuthorize : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
Boolean authorized = Convert.ToBoolean(
HttpContext.Current.Session["UserIsAuthorized"]
);
if (!authorized) {
/* Not logged in so send user to the login page */
filterContext.HttpContext.Response.Redirect("/Login/Login");
}
}
public override void OnActionExecuted(ActionExecutedContext filterContext) {}
public override void OnResultExecuting(ResultExecutingContext filterContext) {}
public override void OnResultExecuted(ResultExecutedContext filterContext) {}
}/*End of Authorize Action Filter*/
Login controller:
public class LoginController : Controller
{
private PhotoDBContext _db = new PhotoDBContext();
public ActionResult Login()
{
string viewName = "";
Boolean authorized = Convert.ToBoolean(Session["UserIsAuthorized"]);
if (authorized)
{
viewName = "../Views/Index";
}
else
{
viewName = "../Views/Login/Login";
}
return View(viewName);
}
[HttpPost]
public ActionResult Login(string pUsername, string pPassword)
{
string viewName = "";
List<Photo> model = new List<Photo>();
var qUsers = from u in _db.Users
select u;
foreach (User user in qUsers.ToList<User>())
{
/* If authorized goto CMS pages */
if (pUsername == user.Username && pPassword == user.Password)
{
Session["UserIsAuthorized"] = true;
var qPhotos = from p in _db.Photos
where p.IsNew == false
select p;
model = qPhotos.ToList<Photo>();
viewName = "../Views/PhotoCMS/Index";
break;
}
}
return View(viewName, model);
}
}/* End of Login controller */
Turns out the whole ASP.Net application was restarting because as part of the photo upload I was storing the image file in a temporary folder and then deleting the directory after moving the file to a permanent location. Apparently its default behaviour for ASP.Net to restart if a directory within the web site is deleted. I found this post
which describes the problem and offers a solution whereby the following code is added to the Global.asax.cs file. Implementing this solution has fixed the problem. The fix is applied by calling FixAppDomainRestartWhenTouchingFiles() from the Application_Start() event:
protected void Application_Start()
{
FixAppDomainRestartWhenTouchingFiles();
}
private void FixAppDomainRestartWhenTouchingFiles()
{
if (GetCurrentTrustLevel() == AspNetHostingPermissionLevel.Unrestricted)
{
/*
From: http://www.aaronblake.co.uk/blog/2009/09/28/bug-fix-application-restarts-on-directory-delete-in-asp-net/
FIX disable AppDomain restart when deleting subdirectory
This code will turn off monitoring from the root website directory.
Monitoring of Bin, App_Themes and other folders will still be
operational, so updated DLLs will still auto deploy.
*/
PropertyInfo p = typeof(HttpRuntime).GetProperty(
"FileChangesMonitor", BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static);
object o = p.GetValue(null, null);
FieldInfo f = o.GetType().GetField(
"_dirMonSubdirs", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.IgnoreCase);
object monitor = f.GetValue(o);
MethodInfo m = monitor.GetType().GetMethod(
"StopMonitoring", BindingFlags.Instance | BindingFlags.NonPublic);
m.Invoke(monitor, new object[] { });
}
}
private AspNetHostingPermissionLevel GetCurrentTrustLevel()
{
foreach (AspNetHostingPermissionLevel trustLevel in
new AspNetHostingPermissionLevel[] {
AspNetHostingPermissionLevel.Unrestricted,
AspNetHostingPermissionLevel.High,
AspNetHostingPermissionLevel.Medium,
AspNetHostingPermissionLevel.Low,
AspNetHostingPermissionLevel.Minimal }
)
{
try
{
new AspNetHostingPermission(trustLevel).Demand();
}
catch (System.Security.SecurityException)
{
continue;
}
return trustLevel;
}
return AspNetHostingPermissionLevel.None;
}
Since sessions are associated with cookies, they are available for a specific domain.
It's a common mistake to ask for a session variable in the same application while the domain has changed (i.e. redirecting to a subdomain).
Does the controller action that you are posting the form contains any [Authorize] attribute. You need to post some code.
Verify a new session is really started every time. Check Trace output for the user's session id to ensure it realllly has changed.
Ensure the cookie getting sent over is actually getting set and sent over. (called ASPsessionIDSOMETHING ) and if that is being sent by the browser. Download the tool Fiddler to check the cookies easily (set cookie header coming from the server and the request cookies going back to the server from the browser. Make sure your browser is accepting the cookie and you dont say... have cookies turned off.
If your session id is changing at every request then your session isn't properly getting set the first time, set a break point on that code if you havent already.
You can log when the worker process resets - ensure that isn't the case. see http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/IIS/87892589-4eda-4003-b4ac-3879eac4bf48.mspx
I had the same problem. The problem only occured when a post request was send to the server and the session was not modified during that request. What I did as a workaround was, to write a custom filter which does nothing more than writing a key / value into the session on each request and added that filter to the GlobalFilter collection in the global.asax.
public class KeepSessionAlive : IActionFilter
{
public void OnActionExecuting(ActionExecutingContext filterContext)
{
if(filterContext.HttpContext.Session != null)
{
filterContext.HttpContext.Session["HeartBeat"] = DateTime.Now.ToShortDateString();
}
}
public void OnActionExecuted(ActionExecutedContext filterContext) { }
}
And in the global.asax:
protected override void AddCustomGlobalFilters(GlobalFilterCollection filters)
{
filters.Add(new KeepSessionAlive());
}
This might be not the best solution but it helped me in my case.
I have a very strange problem: NHibernate crashes when being called from a web user control.
I am working on a ASP.Net (2.0) web page which uses NHibernate to access a database.
And I have a simple factory class to access a column CurrentStepNumber in the table ProjectInfo:
public class ProjectEntity
{
private int? _currentStepNumber;
public virtual int? CurrentStepNumber
{
get { return _currentStepNumber; }
set { _currentStepNumber = value; }
}
public static ProjectWizardEntity GetById(int id, bool shouldLock)
{
return RepositoryFactory.ProjectWizardRepository.GetById(id, shouldLock);
}
public static ProjectWizardEntity GetById(int id)
{
return GetById(id, false);
}
public virtual void Save()
{
RepositoryFactory.ProjectWizardRepository.Save(this);
}
public virtual void SaveOrUpdate()
{
RepositoryFactory.ProjectWizardRepository.SaveOrUpdate(this);
}
}
This class is accessed via a proxy class, so that everytime a new value is assigned it is flushed to the database:
public class DBHelper
{
ProjectEntity _projectEntity;
ProjectEntity GetProjectEntity()
{
if (_projectEntity == null)
_projectEntity = //get or create a new one;
return _projectEntity ;
}
public int? CurrentStepNumber
{
get
{
return (CurrentProjectId > 0) ? CurrentProjectWizardEntity.CurrentStepNumber : 0;
}
set
{
if (CurrentProjectId > 0)
{
CurrentProjectWizardEntity.CurrentStepNumber = value;
CurrentProjectWizardEntity.SaveOrUpdate();
}
}
}
}
Now the problem:
When I access CurrentStepNumber from the test.aspx page, everything works perfectly
When I read this field from the web user control (test.ascx) which is used on test.aspx page it is still OK
However when I try to assign a value to CurrentStepNumber in the code behind the control (test.ascx) I always get an exception:
NHibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session
Actually SaveOrUpdate method of the NHibernate Repository throws the exception.
I could not figure out what could be the problem here, so any help will be appreciated.
I think that You have a session management problem here. How is RepositoryFactory.ProjectWizardRepository.GetById creating and possibly disposing the NHibernate session? Does it create and then close a session?
It seems that DBHelper.GetProjectEntity() is creating or loading a ProjectEntity. Later, when CurrentStepNumber's setter i called, You insert or update the object to the database.
The problem is that when DBHelper.GetProjectEntity() is loading an existing object and later closing the session after it has been loaded but keep the object around, we are entering deep water. When the object is later updated, You set a new value for CurrentStepNumber and send the object to NHibernate to save. The problem here is that the object is not associated with the new session that is created and closed during saving. Nhibernate then gets confused since a new object is discovered that is not loaded from current session but it has an id of an existing object.
For a solution, Google for "NHibernate asp.net session management" and You will get a number of good hits about how to use the ASP.NET request cycle as a unit of work.
I am working on a project management web application. The user has a variety of ways to display a list of tasks. When viewing a list page, they click on task and are redirected to the task edit page.
Since they are coming from a variety of ways, I am just curious as to the best way to redirect the user back to the calling page. I have some ideas, but would like to get other developers input.
Would you store the calling url in session? as a cookie? I like the concept of using an object handle the redirection.
I would store the referring URL using the ViewState. Storing this outside the scope of the page (i.e. in the Session state or cookie) may cause problems if more than one browser window is open.
The example below validates that the page was called internally (i.e. not requested directly) and bounces back to the referring page after the user submits their response.
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (Request.UrlReferrer == null)
{
//Handle the case where the page is requested directly
throw new Exception("This page has been called without a referring page");
}
if (!IsPostBack)
{
ReturnUrl = Request.UrlReferrer.PathAndQuery;
}
}
public string ReturnUrl
{
get { return ViewState["returnUrl"].ToString(); }
set { ViewState["returnUrl"] = value; }
}
protected void btn_Click(object sender, EventArgs e)
{
//Do what you need to do to save the page
//...
//Go back to calling page
Response.Redirect(ReturnUrl, true);
}
}
This message my be tagged asp.net but I think it is a platform independent issue that pains all new web developers as they seek a 'clean' way to do this.
I think the two options in achieving this are:
A param in the url
A url stored in the session
I don't like the url method, it is a bit messy, and you have to remember to include the param in every relevent URL.
I'd just use an object with static methods for this. The object would wrap around the session item you use to store redirect URLS.
The methods would probably be as follows (all public static):
setRedirectUrl(string URL)
doRedirect(string defaultURL)
setRedirectUrl would be called in any action that produces links / forms which need to redirect to a given url. So say you had a projects view action that generates a list of projects, each with tasks that can be performed on them (e.g. delete, edit) you would call RedirectClass.setRedirectUrl("/project/view-all") in the code for this action.
Then lets say the user clicks delete, they need to be redirected to the view page after a delete action, so in the delete action you would call RedirectClass.setRedirectUrl("/project/view-all"). This method would look to see if the redirect variable was set in the session. If so redirect to that URL. If not, redirect to the default url (the string passed to the setRedirectUrl method).
I agree with "rmbarnes.myopenid.com" regarding this issue as being platform independent.
I would store the calling page URL in the QueryString or in a hidden field (for example in ViewState for ASP.NET). If you will store it outside of the page scope (such as Session, global variable - Application State and so on) then it will not be just overkill as Tom said but it will bring you trouble.
What kind of trouble? Trouble if the user has more than one tab (window) of that browser open. The tabs (or windows) of the same browser will probably share the same session and the redirection will not be the one expected and all the user will feel is that it is a bug.
My 2 eurocents..
I personally would store the required redirection info in an object and handle globally. I would avoid using a QueryString param or the like since they could try bouncing themselves back to a page they are not supposed to (possible security issue?). You could then create a static method to handle the redirection object, which could read the information and act accordingly. This encapsulates your redirection process within one page.
Using an object also means you can later extend it if required (such as adding return messages and other info).
For example (this is a 2 minute rough guideline BTW!):
public partial class _Default : System.Web.UI.Page
{
void Redirect(string url, string messsage)
{
RedirectionParams paras = new RedirectionParams(url, messsage);
RedirectionHandler(paras); // pass to some global method (or this could BE the global method)
}
protected void Button1_Click(object sender, EventArgs e)
{
Redirect("mypage.aspx", "you have been redirected");
}
}
public class RedirectionParams
{
private string _url;
public string URL
{
get { return _url; }
set { _url = value; }
}
private string _message;
public string Message
{
get { return _message; }
set { _message = value; }
}
public RedirectionParams(string url, string message)
{
this.URL = url;
this.Message = message;
}
}